The Grammy Award winner, 30, attended the "Batman Live" premiere in Los Angeles with her husband, Eddie Cibrian, 39, and stepsons, Mason, 9, and Jake, 5. The family outing took place nearly one month after Rimes sought treatment for anxiety and stress.

The foursome kept things light at the premiere, painting mustaches on their index fingers and holding them above their upper lips for photographers. Before their arrival, Rimes -- wearing head-to-toe black -- shared a photo of herself wearing cat ears with her Twitter followers. "Channeling my inner Catwoman for Batman Live," she wrote.

Despite entering an in-patient treatment facility in August, Rimes has left several times due to work obligations. She performed in Eau Claire, Wis., on Sept. 7, and sang during VH1 Save The Music Foundation's Songwriters Music Series in Napa, Calif., on Sept. 20.

Though Rimes' rep told Us Weekly the "Blue" singer decided to seek treatment "to learn and develop coping mechanisms" for stressful situations, a source later revealed it was because "LeAnn makes herself sick with worry about Eddie carousing. It's all become too much for her."

When Us first reported Rimes' affair with her "Northern Lights" costar in 2009, Cibrian was married to "Real Housewives of Beverly Hills" star Brandi Glanville, 39. Rimes was also wed at the time, to dancer Dean Sheremet, 31.

"She's afraid Eddie will always be a cheater," a family friend recently explained. "She keeps reading rumors about Eddie cheating on her and has started believing them."

Rimes is currently finishing up her 12th album, "Spitfire" -- which she hopes will reinvigorate her career as a country music superstar. "After the cheating scandal, her career was never the same -- and she is still faced with so much criticism," an insider told Us. "She thought it would go away, but it hasn't."